System for performing carrier return operation

ABSTRACT

A system for performing a carrier return operation in a typewriter, printer, etc., having a leadscrew controlled carrier, and controlling when the carrier is to be returned dependent upon a carrier return signal generated in conjunction with combinations of generated signals indicative of rotation and nonrotation of the leadscrew, and the leadscrew rotational position. The system is structured such that the carrier will be returned and properly positioned at the left margin or starting line upon termination of escapement, and upon signals being generated indicating that the leadscrew is in its home rotational position.

United States Patent 1191 Morrison et a1.

14 1 Dec. 18,1973

SYSTEM FOR PERFORMING CARRIER RETURN OPERATION Inventors: Donald J;Morrison; Reuben Raesz,

both of Austin, Tex.

International Business Machines Corporation, Armonk, NY.

Filed: on. 22, 1971 Appl. No.2 191,679

Assignee:

us. c1 197/66, 197/19, 197/84 R, 197/90, 197/91, 197/176, 340/172.5

11m. c1 B41j 19/70 Field 61 Search 197/16, 19, 20, 65, 197/66, 67, 68,s2, s4, 84 A, 84 B, 89,90,

References Cited UNITED STATES PATENTS 10/1967 Cralle et al. 197/176 X2/1941 Bernhard 197/84 A 12/1953 Frey et al.,.. 197/84 B 5/1959 Frey197/84 B 9/1959 Walton et al. 197/66 7/1966 Bell 1 1. 340/203 9/1968Perkins et a1. 340/1725 3,406,625 Chamness et al 197/90 UX 3.512,]325/1970 Jones et al. 197/84 R X 3,588,119 6/1971 3,647,041 3/1972 Daviset a]. 197/84 A X OTHER PUBLICATIONS IBM Technical Disclosure Bulletin,Printer with High-Speed Space Control, H. C. Tanner, Vol. 12, No. 12,May 1970, pp. 2260-2261.

Primary Examiner Ernest T. Wright, Jr. Attorney.lames l-l. Barksdale,Jr. et a1.

57 ABSTRACT A system for performing a carrier return operation in atypewriter, printer, etc., having a leadscrew controlled carrier, andcontrolling when the carrier is to be returned dependent upon a carrierreturn signal generated in conjunction with combinations of generatedsignals indicative of rotation and non-rotation of the leadscrew, andthe leadscrew rotational position, The system is structured such thatthe carrier will be returned and properly positioned at the left marginof starting line upon termination of escapement, and upon signals beinggenerated indicating that the leadscrew is in its home rotationalposition.

12 Claims, 5 Drawing Figures PMENTEB HEB 18 973 sum 10F 2 EMITTER HOMECOMBINATION GEAR TYPEWRITER FIG. 2

SYSTEM FOR PERFORMING CARRIER RETURN OPERATION BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally tocarrier return systems in typewriters having a leadscrew controlledcarrier, and more specifically to a system for performing a carrierreturn operation wherein signal sequences and combinations related tocarrier escapement and the leadscrew rotational position in conjunctionwith a carrier return signal control when the carrier is to be returned.

2. Description of the Prior Art Heretofore, much of the prior art hasdealt mainly with movable carriage type typewriters with the primaryconcern being the return of the carriage in such a manner as to reduceshock, vibration, and resulting breakage. With the increasing popularityof carrier type typewriters having a carrier under the control of aleadscrew, attention has been given to the problem of homing theleadscrew to insure that the carrier is in engagement with the threadsof the leadscrew when 'it is positioned at the starting line or leftmargin.

Representative of the closest known prior art is U. S. Pat. No.3,346,088. Disclosed is a single element typewriter having a carrier anda leadscrew which must be horned or rotated to a predeterminedrotational position to correctly position the carrier at the end of acarrier return operation. The homing operation involves the steps ofremoving escapement and holding pawls from a pin wheel, allowing theleadscrew to rotate in a direction to advance the carrier, sensing whenthe leadscrew has reached a home position, and re-engaging theescapement and holding pawls with the pin wheel. Sensing is by means ofa sensing pawl engaging oppositely disposed and radially projectinghoming lugs on a homing disc.

' In the event the leadscrew is in its home rotational position at thetime a carrier return is keyed, the sensing pawl engages one of theradially projecting homing lugs andthe escapement and holding pawls arenot withdrawn from the pin wheel. In this event, the leadscrew is notrotated, is already homed, and the carrier is returned.

With the system of this invention, the apparatus for performing otheroperations is also utilized for performing a carrier return operation.For example, the emitter wheel and associated sensor can also be usedfor tabular operations, for determining the measure, for determining theposition of the carrier, for determining the extent of escapement, etc.,while the ratchet gear and associated magnet-armature assembly can alsobe used for terminating character, tab, and space escapement. Inessence, a carrier return operation is accomplished electronically andtakes advantage of existing apparatus, thus not increasing thelikelihood of mechanical failure through incorporation of additionalmechanical apparatus.

BRIEF DESCRIPTION OF DRAWING FIG. I shows a typewriter carrier and meansfor urging the carrier in the advancing and return directions, and aleadscrew and an associated emitter wheel and ratchet gear forcontrolling advancement of the carrier.

FIG. 2 is a more detailed view of the emitter wheel and an associatedsensing device.

FIG. 3 is a more detailed view of the ratchet gear and an associatedmagnet-armature assembly.

FIG. 4 is a timing diagram showing the relationship of sensed spokes onthe emitter wheel and the teeth on the ratchet gear.

FIG. 5 is a block diagram depicting the apparatus for performing acarrier return operation and controlling when the carrier is to bereturned.

SUMMARY OF THE INVENTION Briefly, means are provided for generating andrecognizing signal combinations in conjunction with a carrier returnsignal for the purposes of insuring that the leadscrew controlling thecarrier in a carrier type type writer has been horned prior to effectingthe return of the carrier. The signal combinations are dependent uponrotation and non-rotation of the leadscrew and the leadscrew rotationalposition. The system is such that a carrier return signal can begenerated from a keyboard or a record reader and that the return of thecarrier will not take place until carrier escapement in either directionfor previously keyed or read characters and functions has terminated.Upon termination of a previous character or function escapement, acarrier return signal and a home signal indicative of the homerotational position of the leadscrew will cause the carrier to return tothe left margin or starting line. Since the leadscrew has been horned,when the carrier is returned to the left margin the threads on theleadscrew will be engaged and the carrier will be maintained at thatposition until escapement is again initiated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS or in the advancing direction,by cable 29 which follows a path around pulley 18, which is connected tocable tensioning arm 17, and over pulley 19 to windup block 20. Forceapplied to carrier 16 by cable 29 is supplied by mainspring 27maintained by mounting plate 26. Since carrier 16 is driven, orimpelled, to the right by mainspring 27 and cable 29, and since mountingbracket 7 carrying pivotable shoe 6 is secured to carrier 16 withpivotable shoe 6 engaging the threads of leascrew 1, carrier advancementis controlled by counterclockwise rotation of leadscrew I (as viewedfrom the end having ratchet gear 32) under the influence of a gear trainand power means not shown. For backspace operations, rotation ofleadscrew l in the reverse, or clockwise, direction is initiated bymeans of a backspace magnet and spring clutch assembly not shown in FIG.1.

The return of carrier 16 to the left for a carrier return operationresults in pivotable shoe 6 pivoting and ratcheting over the threads ofleadscrew 1. Carrier 16 is driven to the left, or in the returndirection, for a carrier return operation by cable 30 which follows apath around pulleys 14, 13 and over pulley 25 to windup block 24. Forceis applied by cable 30 through gears 22 and 23 by means of shaft 21connected to a motor or other power means not shown, and thetransmission of power through shaft 21 will also effect windup ofmainspring 27.

As shown in FIG. 1, the leadscrew 1 has an emitter wheel 31 on one'endand a ratchet gear 32 on the other end. Ratchet gear 32 and teeth 2 haveassociated therewith a magnet-armature assembly comprising armature 3biased by spring 4 over fulcrum member 28, and electro-magnet 5. Whenforward rotation of leadscrew 1 is to be stopped, electro-magnet 5 isdeactivated, allowing armature 3 to contact and abut the teeth 2 onratchet gear 32.

Emitter wheel 31 on the left end of leadscrew 1 has emitter spokes 9 anda home emitter spoke 8, and has an associated sensing device 10containing a home sensor 126 and an emitter sensor 127 for sensing thepassage therethrough of emitter spokes 9 and home emitter spoke 8, andproviding signals indicative thereof. Lead wires 12 carry pulsesindicating the sensing of the home emitter spoke 8 and lead wires 11carry pulses indicating the sensing of emitter spokes 9. Lead wires 1 1and 12 are connected to the remainder of the system as will be describedwith reference to FIG. 5.

Referring to FIGS. 2 and 3, emitter wheel 31 and ratchet gear 32 areshown in more detail illustrating the correspondence of home emitterspoke 8 and home lug 38 of teeth 2. Emitter wheel 31 and ratchet gear 32are viewed from the end of leadscrew 1 having ratchet gear 32. A timingdiagram is shown in FIG. 4 showing the relationship of ratchet gear 32and signals generated upon the sensing of home emitter and emitterspokes 8 and 9 on emitter wheel 31. When home emitter spoke 8 is sensed,the home and emitter sensors 126 and 127 both provide signals due to thestructure of the home emitter spoke 8, and these two signals arecombined. The combination signal will for a carrier return operationcontrol electro-magnet 5, which upon deactivation will allow armature 3to contact lug 37 of teeth 2 and thereafter abut surface 39 of home lug38 of teeth 2 stopping rotation of leadscrew 1. Surface 39, lug 37, andhome lug 38 have been described separately for purposes of clarity. Inactual practice, as far as the actual structure of the ratchet gear 32,per se, is concerned, surface 39 is identical to surfaces 33 and lug 37and home lug 38 are identical to lugs 34. That is, ratchet gear 32 issymmetrical with respect to its axis of rotation. The combination signalwill remain up until electro-magnet 5 is again activated and rotation ofleadscrew 1 is initiated. This relationship will become more readilyapparent upon reading the remainder of the specification.

With the above serving as background, reference is made to FIG. 5 inconjunction with FIGS. 1-4. In FIG. 5 there is shown a printer ortypewriter keyboard 41 and record reader 42, either of which serves as asource of character and function output, providing signals to theremainder of the system. Characters are defined herein to be charactersand spaces, while the functions referred to herein are defined to betab, backspace, and carrier return. Reference is made herein to both upand down signals, and the lack of reference to a signal being either up"or down" is to be taken as up." In more conventional terminology, up"and down are taken as positive and negative logical levels,respectively. Further, reference to a Not signal is to be taken asdown." In any event, signal is hereinafter to be taken as an electricalor electronic signal.

Assembly 50 is made up of apparatus described above. That is, leadscrewl is shown in FIG. 1, the home and emitter sensors 126 and 127 make upsensing device 10 shown in FIG. 1, emitter wheel 31 is shown in FIGS. 1and 2, the forward escapement magnet is shown as electro-magnet 5 inFIG. 1, the ratchet gear 32 is shown in FIGS. 1 and 3, the armatureassembly is shown in FIGS. 1 and 3 and is made up of armature 3, spring4, and fulcrum 28, and the backspace magnet and spring clutch assemblyreferred to above for effecting reverse rotation of leadscrew 1 has notbeen shown in FIG. 1 in order to avoid confusion. The structure of this,or a similar apparatus, is well known to those skilled in the art; beingcomprised of a magnet, armature, gear train, and spring clutch.

The signal combinations to be considered in conjunction with a carrierreturn signal (CR) are a home signal (HOME) and a Not rotational signal(ROTATION or E S HOME and a rotation signal (ROTATION or ESC), ROTATIONand a Not home signal (HOME), and ROTATION and HOME. The carrier returnsignal is generated from printer keyboard 41 upon the operator keying acarrier return or from record reader 42 reading codes on a recordingmedia.

Not Rotation and Not Home (ESC and HOME) A carrier return signalgenerated upon a carrier return being keyed on printer keyboard 41 by anoperator, or being read from a recording media by record reader 42, andapplied along lines 43 or 44, respectively, gated through OR gate 45,and applied along lines 46, 128, and 97 when leadscrew 1 is not rotatingand carrier 16 is not escaping (ES? applied along line 98 from inverter122), and when leadscrew 1 is not in its home rotational position (HOMEapplied along line 99 from inverter will result in a signal appliedalong line 101 from AND gate 100. The signal applied along line 101 isto spaced encode 102 which causes space encode 102 to output a spacealong line 105, through OR gate 107, and along line 108 for storage inescapement register 58. Space encode 102 is structured to output a spacehaving a three-unit escapement value count. This stored count is appliedalong line 56 to comparator 54 and there compared with the count ofemitter pulses applied to comparator 54 along line 53 from escapementcounter 52. Emitter pulses sensed upon rotation of leadscrew 1 by theemitter sensor (127 in FIG. 1) of assembly 50 are applied along a singlerepresentative line 49 (lines 11 in in FIGS. 1 and 2) to escapementcounter 52. E'scapement counter 52 and escapement register 58 areresettable, and are reset along lines 1 13 and 114, respectively, eachtime a signal is applied along line 55 which occurs when the contents ofescapement counter 52 are greater than, or equal to, the contents ofescapement register 58. Leadscrew 1 will not be stopped until the countin escapement counter 52 is equal to, or exceeds, the count for a space,or a previous character or function. When leadscrew 1 is stopped,escapement counter 52 and escapement register 58 will have been reset tozero for input and accumulation of the count for the next character orfunction.

With a three-unit space input to the escapement register 58, comparator54 will bring up lines 57 and 59 when the count-in escapement counter 52is less than the count inescapement register 58. This will set characterescapement latch 63 which is reset upon termination of escapement forany previous character or function as will be described in more detailbelow. Upon the setting of character escapement latch 63, a signal isapplied along line 64, through OR gate 66, and thence along line 67 tothe forward escapement magnet in assembly 50. A pointed out above, theforward escapement magnet in assembly 50 corresponds to electromagnet 5in FIG. 1. The signal applied along line 67 is an initiation signal andcauses the forward escapement magnet in assembly 50 to be activated,disengaging armature 3 from ratchet gear 32, and initiating or allowing,rotation of leadscrew 1 and escapement of carrier 16.

When the count in escapement counter 52 exceeds, or equals, the count inescapement register 58 (B B A=3 a signal is applied along lines 55 and92 providing one of the inputs to NAND gate 94. NAND gate 94 derives itsother input from NAND gate 91 along line 93. The sensing thereafter of ahome emitter spoke (8 in FIG. 1) by the home sensor (126 in FIG. 1) inassembly 50 will cause a home signal to be applied along a singlerepresentation line 48 (line 12 in FIGS. 1 and 2). This signal isinverted by an inverter 120 and a down signal is applied along lines 129and 89 to NAND gate 91. With the signal for carrier return applied alonglines 46, 130 and 90 being up and with a Not reverse escapement signalapplied along line 88 being up, due to a down signal appearing on line110 having been inverted by an inverter 121, the output of NAND gate 91along line 93 will be up. The up signals now applied along lines 92 and93 are inverted by NAND gate 94 and a down signal is applied along line95 resetting character escapement latch 63. Upon character escapementlatch 63 being reset, the forward escapement magnet in assembly 50 isdeactivated, stopping rotation of leadscrew 1 through a signal appliedalong line 64, through OR gate 66, and along line 67. Thus, rotation ofleadscrew l and forward escapement of carrier 16 will occur until a homesignal appears on line 48. Then if the contents of escapement counter 52are equal to, or greater than, the contents of escapement register 58,character escapement latch 63 will be reset. If however, a home signalhad not appeared on line 48 by the time a B 2 A signal appeared on line55, leadscrew 1 would continue rotating since all input conditions toNAND gate 91 would be up resulting in a down input into NAND gate 94which would cause a positive logical level to be applied to characterescapement latch 63. Character escapement latch 63 would not be resetsince a down signal along line 95 is required for resetting.

When character escapement latch 63 is reset, the condition foractivating carrier return and index magnets 83 is met clue to a carrierreturn signal applied along lines 46, 128, 131, and 132, a ET signalresulting from a down signal along lines 68 and 133 which is inverted byan inverter 122 and applied along line 134, and a home signal appliedalong lines 48 and 135, applied along lines 87, 86, and 85,respectively, through AND gate 109 and along line 84. With the carrierreturn and index magnets 83 activated, carrier 16 is caused to returnthrough a force applied to carrier 16 by cable 30 shown in FIG. 1, andthe typewriter platen (not shown) is indexed.

With leadscrew 1 being in its home rotational position when carrier 16is returned to the left margin, pivotable shoe 6, which ratchets overthe leadscrew l during a carrier return operation, will engage thethreads on leadscrew 1 and maintain carrier 16 at the left margin. lfleadscrew 1 were not in its home rotational position and carrier 16 werereturned, upon deactivation of carrier return and index magnets 83,carrier 16 would be displaced in the advancing direction a shortdistance until pivotable shoe 6 engaged the threads on leadscrew 1, andtherefore, would not be positioned at the starting line or left margin.Such an event would result in an uneven left side on output, and this isto be overcome with the system of this invention.

Home and Not Rotation (HOME and 58C) The next to last paragraph above inthe description of ESC and HOME is pertinent to the conditions of HOMEand ESC. Again, when character escapement Not Home and Rotation (HOMEand ESC) The condition, or signal combinations, of leadscrew rotationand Not home can be divided into four categories determined by the causeof rotation of leadscrew 1. If leadscrew 1 is rotating, this is becausecarrier 16 is escaping for a previously keyed or read character, space,tab, backspace, etc., and rotation of leadscrew 1 and escapement ofcarrier 16 will continue for this previously read character or functionuntil completed, and then the carrier return signal appearing initiallyon line 46 will be recognized.

These four categories are as follows:

1. Repeat Carrier Return Referring to the discussion related to m andHOME, after the three-unit space has been input to escapement register58 and rotation of leadscrew 1 has been initiated, carrier escapementlatch 63 is reset as described, with carrier return and index magnets 83being activated. At this time, the conditions EG and HOME are met andcarrier 16 is returned. During the returnof carrier 16, leadscrew l isnot rotating, is in its home rotational position, and the resetcondition for resetting carrier escapement latch 63 is still met. Arepeat carrier return signal on line 46 will effectively only result inthe indexing of the printer or typewriter platen (not shown) uponcarrier return and index magnets 83 being activated again.

2. Tab Operation When leadscrew 1 is rotating due to a tab functionhaving been keyed or read, this rotation was caused by a signalappearing on lines 46, 128, 131 and 112 causing space encode 102 toinput a 3 unit space into escapement register 58 as described above inrelation to ES?) and HOME.

In further describing the forward escapement magnet of assembly 50(electro-magnet 5 in FIG. ll), it is controlled by either characterescapement latch 63 or tab escapement latch 70, with the last inputhaving control thereof through OR gate 66. That is, during tabescapement of carrier 16, a signal applied along line resettingcharacter escapement latch 63 will not deactivate the forward escapementmagnet during rotation of leadscrew 1 when escapement or rotationsignals are applied along lines 68 and 73 in conjunction with the tabfunction signal applied along lines 46, and 74.

These signals are gated through AND gate 72 and applied along line 71setting tab escapement latch 70 and causing continued activation of theforward escapement magnet of assembly 50 due to the output of tabescapement latch 70 applied along line 69, through OR gate 66 and alongline 67. The signal now applied along line 67 is a continuation signal.

After carrier 16 has escaped 3 units upon rotation of leadscrew 1, asignal appears on lines 55 and 81. Thereafter, when carrier 16 contactsa tab stop contact 123 and a signal indicative thereof is applied alongline 80, and a subsequent, or coincidental, home signal appears on line.79, a signal is gated through NAND gate 78, and inverted, by inverter124, providing the down signal applied along line 77 for resetting tabescapement latch 70 and deactivating the forward escapement magnet ofassembly 50. The CR, W, and HOME signals then applied along lines 87,86, and 85, respectively, are gated through AND gate 109 and along line84 for activating carrier return and index magnets 83 for causingcarrier 16 to return.

3. Characters and Spaces When rotation of leadscrew 1 is due to acharacter or space having been keyed or read prior to a carrier returnsignal being keyed or read, the count of the character or space is inputalong lines 46, 128, 131, 132, and 103 to previous character andfunction register 104 which is resettable to zero each time rotation ofleadscrew 1 is stopped. This count is applied along line 106, through ORgate 107, and along line 108 and stored in escapement register 58. Theremainder of the operation is as described in the description related toF8? and HOME. That is, when character escapement latch 63 has beenreset, and when leadscrew 1 is not rotating and is in its homerotational position, signals indicative thereof applied along lines 86and 85, respectively, will be gated through AND gate 109 when a carrierreturn signal appears on lines 46, 128, 131, 132 and 87. The signal thenapplied along line 84 will activate carrier return and index magnets 83for causing carrier 16 to return.

4. Backspace Operation When rotation of leadscrew 1 is the result of abackspace having been keyed or read prior to a carrier return signalbeing generated, a backspace signal appeared on lines 46, 128, 131, 132and 103 with the escapement value count thereof being accumulated inprevious character and function register 104. This count was appliedalong line 106, through OR gate 107, and along line 108, and stored inescapement register 58. Until the count in escapement counter 52 for thenumber of emitter pulses appearing on line 49 was equal to, or greaterthan, the backspace count stored in escapement register 58, a signalappeared on lines 57 and 60. This signal in conjunction with thebackspace operation signal on line 61 caused a signal to be gatedthrough AND gate 117 and along lines 62 136, activating the backspacemagnet and spring clutch assembly of assembly 50 and causing reverserotation of leadscrew l and reverse escapement of carrier 16. The signalapplied along line 57 also appeared on line 59, setting escapement latch63.

It is not necessary to set carrier escapement latch 63 and activate theforward escapement magnet of assembly 50 for a backspace operation since(as can be seen in FIG. 3) armature 3 will ratchet over teeth 2 whenelectro-magnet 5 is deactivated and leadscrew 1 is rotated in aclockwise direction. Noise is reduced, and therefore, characterescapement latch 63 is set and forward escapement magnet of assembly 50is activated.

As mentioned, with a B A signal appearing on line 60 and a backspaceoperation signal appearing on line 61, a signal is gated through ANDgate 117 and along lines 62 and 136 to activate the backspace magnet andspring clutch assembly of assembly 50 to cause reverse, or clockwise,rotation of leadscrew 1. Thereafter, when a B 2 A signal appears on line55, escapement counter 52 and escapement register 58 are reset to zeroalong lines 113 and 114, respectively, and an up signal is applied alongline 92 to NAND gate 94. The other input to NAND gate 94 along line 93is also up since the signal appearing along line 88 is down (due to theup signal appearing on line 110 having been inverted by inverter 121) atthe time the NOT home signal applied I along line 89 is either up ordown and the carrier return signal along line 90 is up. The resultingdown signal output from NAND gate 94 is applied along line 95 forresetting carrier escapement latch 63 and deactivating the forwardescapement magnet of assembly 50. As pointed out above, deactivation ofthe forward escapement magnet of assembly 50 does not stop reverserotation of leadscrew 1 since armature 3 ratchets over teeth 2 onratchet gear 32. The stopping of leadscrew 1 takes place when the signalapplied along line 57 is no longer up for activating the backspacemagnet and spring clutch assembly of assembly 50. The resetting ofcharacter escapement latch 63 and the deactivation of the forwardescapement magnet of assembly 50 prevents forward rotation of leadscrew1 when the backspace magnet and spring clutch assembly of assembly 50 isdeactivated.

With leadscrew 1 now stopped, the signals CR, 1 18C, and W. appliedalong lines 97, 98, and 99, respectively, are gated through AND gate andalong line 101 to space encode 102 for initiating forward escapement andthe subsequent return of the carrier 16 as described above.

A backspace latch could be included in the above system to insure theforward homing of leadscrew 1. That is, a backspace latch could be usedto insure that the return of carrier 16 will only follow forwardescapement. As now shown, a down signal on line 57 causing leadscrew 1to stop reverse rotation in conjunction with a home signal would satisfythe conditions for gating a signal through AND gate 109 and along line84, activating carrier return and index magnets 83 and causing carrier16 to return.

Home and Rotation (HOME and ESC) lf leadscrew 1 is rotating and in itshome rotational position at the time a carrier return signal appears online 46 and a B 2 A signal appears on lines 55 and 92, characterescapement latch 63 will be reset, stopping rotation of leadscrew 1 andactivating carrier return and index magnets 83 as described above. Ifescapement of carrier 16 and rotation of leadscrew 1 for the previouscharacter or function have not been completed and a home signal appearson line 48, character escapement latch 63, or tab escapement latch 70will remain set, with leadscrew l continuing to rotate until a signalappears on line 55. A home signal appearing coincident therewith, orthereafter, will cause character escapement latch 63 to be reset andcarrier return and index magnets 83 to be activated. Tab escapementlatch 70 will not be reset until a tab contact signal appears on line80, and a home signal appears coincident therewith, or thereafter, online 79.

In summary, it is the combination of signals indicative of therotational position of leadscrew 1 and rotation and non-rotation ofleadscrew l in conjunction with, or following, a carrier return signalwhich forms the basis for determining when the leadscrew 1 is to behorned, when the leadscrew 1 is home, and when the carrier 16 is to bereturned. In all cases, escapement for a previous character or functionmust have terminated, rotation of leadscrew 1 must have stopped, and theleadscrew 1 must be in its home rotational position before a carrierreturn operation can take place.

With the above described system, when the carrier I 16 has been returnedto the left margin or starting line and the carrier return and indexmagnets 83 have been deactivated, the leadscrew 1 will be in its homerotational position and the pivotable shoe 6 will engage the threads onthe leadscrew 1 and the carrier 16 will be positioned and maintained atthe left margin.

While the invention has been shown and described with reference to aparticular embodiment, it will be understood by those skilled in the artthat various changes in form and detail may be made without departingfrom the spirit and scope of the invention.

What is claimed is:

l. A system for performing a carrier return operation in typewriters,printers, and similar apparatuses having a leadscrew controlling acarrier, said system comprising:

a first means for generating an electronic carrier re turn signal; 1

a second means for generating electronic position signals correspondingto the rotational position of said leadscrew;

a third means for generating electronic rotation and Not-rotationsignals corresponding to rotation and non-rotation of said leadscrew;and

a fourth means for causing said carrier to return upon the occurrence ofan electronic Not-rotation signal and an electronic position signalbeing an electronic home signal corresponding to the home rotationalposition of said leadscrew after an electronic carrier return signal isgenerated.

2. Asystem according to claim 1 wherein said fourth means includes meansfor stopping rotation of said leadscrew upon the occurrence of anelectronic home signal.

3. A system according to claim 2 wherein said fourth means includesmeans for continuing rotation of said leadscrew upon the occurrence ofan electronic position signal not being an electrode home signal untilthe occurrence of an electronic position signal being an electronic homesignal.

4. A system according to claim 2 wherein said fourth means includesmeans for initiating and continuing rotation of said leadscrew upon theoccurrence of an electronic Not-rotation signal and and an electronicposition signal not being an electronic home signal until the occurrenceof an electronic position signal being an electronic home signal.

5. A system for performing a carrier return operation in typewriters,printers, and similar apparatuses having a leadscrew controlling acarrier, said system comprising:

means for generating an electronic carrier return signal;

means for generating electronic position signals corresponding to therotational position of said leadscrew;

means for generating electronic rotation and Notrotation signalscorresponding to rotation and nonrotation of said leadscrew;

means for generating an electronic stop signal and means for-stoppingrotation of said leadscrew;

means for generating an electronic initiation signal and means forinitiating rotation of said leadscrew;

means for generating an electronic continuation signal and means forcontinuing rotation of said leadscrew; and

means for causing said carrier to return upon the occurrence of anelectronic carrier return and any of the following combinations ofelectronic signals:

A. a Not'rotation signal and a home signal corresponding to the homerotational position of said leadscrew;

B. a rotation signal, a home signal, and a stop signal;

C. a rotation signal, a position signal not being a home signal, acontinuation signal, a home signal, and a stop signal;

D. a position signal not being a home signal, a Notrotation signal, aninitiation signal, a home signal, and a stop signal.

6. A system according to claim 5 wherein said means for initiatingrotation of said leadscrew includes means for inputting a space count.

7. A system according to claim 5 wherein said combinations of electronicsignals occur upon forward escapement of said carrier.

g. A system according to claim 5 further including means for determiningforward escapement of said carrier.

9. A system according to claim 5 further including means for continuingcarrier escapement and leadscrew rotation for characters and functionsinput prior to generation of an electronic carrier return signal.

10. A system according to claim 6 further including means for comparingsaid space count with the number of said electronic position signals fordetermining when said carrier is to be returned.

11. A system according to claim 8 further including means fordetermining reverse rotation of the leadscrew.

12. A system according to claim 5 further including means for causingsaid leadscrew to rotate to a home rotational position for saidcombinations of electronic signals (C) and (D).

22 9 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,779,359 Dated December 18, 1973 Inventor) Donald J Morrison, ReubenRaesz It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 9, line 52, the word "electrode" should read -electronic-- .1Column 10, line 23, the word "signal" should be inserted following"return".

Signed and sealed this 9th day of April 1971 (SEAL) Attest:

EDWARD MJ 'LETCHER R. o. MARSHALL DANN Attesting Officer- Commissionerof Patents

1. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising: a first means for generating an electronic carrier return signal; a second means for generating electronic position signals corresponding to the rotational position of said leadscrew; a third means for generating electronic rotation and Notrotation signals corresponding to rotation and non-rotation of said leadscrew; and a fourth means for causing said carrier to return upon the occurrence of an electronic Not-rotation signal and an electronic position signal being an electronic home signal corresponding to the home rotational position of said leadscrew after an electronic carrier return signal is generated.
 2. A system according to claim 1 wherein said fourth means includes means for stopping rotation of said leadscrew upon the occurrence of an electronic home signal.
 3. A system according to claim 2 wherein said fourth means includes means for continuing rotation of said leadscrew upon the occurrence of an electronic position signal not being an electrode home signal until the occurrence of an electronic position signal being an electronic home signal.
 4. A system according to claim 2 wherein said fourth means includes means for initiating and continuing rotation of said leadscrew upon the occurrence of an electronic Not-rotation signal and and an electronic position signal not being an electronic home signal until the occurrenCe of an electronic position signal being an electronic home signal.
 5. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising: means for generating an electronic carrier return signal; means for generating electronic position signals corresponding to the rotational position of said leadscrew; means for generating electronic rotation and Not-rotation signals corresponding to rotation and non-rotation of said leadscrew; means for generating an electronic stop signal and means for stopping rotation of said leadscrew; means for generating an electronic initiation signal and means for initiating rotation of said leadscrew; means for generating an electronic continuation signal and means for continuing rotation of said leadscrew; and means for causing said carrier to return upon the occurrence of an electronic carrier return and any of the following combinations of electronic signals: A. a Not-rotation signal and a home signal corresponding to the home rotational position of said leadscrew; B. a rotation signal, a home signal, and a stop signal; C. a rotation signal, a position signal not being a home signal, a continuation signal, a home signal, and a stop signal; D. a position signal not being a home signal, a Not-rotation signal, an initiation signal, a home signal, and a stop signal.
 6. A system according to claim 5 wherein said means for initiating rotation of said leadscrew includes means for inputting a space count.
 7. A system according to claim 5 wherein said combinations of electronic signals occur upon forward escapement of said carrier.
 8. A system according to claim 5 further including means for determining forward escapement of said carrier.
 9. A system according to claim 5 further including means for continuing carrier escapement and leadscrew rotation for characters and functions input prior to generation of an electronic carrier return signal.
 10. A system according to claim 6 further including means for comparing said space count with the number of said electronic position signals for determining when said carrier is to be returned.
 11. A system according to claim 8 further including means for determining reverse rotation of the leadscrew.
 12. A system according to claim 5 further including means for causing said leadscrew to rotate to a home rotational position for said combinations of electronic signals (C) and (D). 